diff --git a/util/crossgcc/buildgcc b/util/crossgcc/buildgcc
index be5493d16f..cfcd44e8a7 100755
--- a/util/crossgcc/buildgcc
+++ b/util/crossgcc/buildgcc
@@ -49,7 +49,7 @@ NASM_VERSION=2.16.03	# x86 assembly
 IASL_VERSION=20250807	# ACPI compiler
 
 # Clang/LLVM Toolchain (alternative to GCC, built separately)
-CLANG_VERSION=18.1.8
+CLANG_VERSION=21.1.8
 CMAKE_VERSION=4.0.3	# Required for building Clang
 
 # Architecture-specific options
@@ -72,6 +72,7 @@ CTE_ARCHIVE="clang-tools-extra-${CLANG_VERSION}.src.tar.xz"
 LLVMCMAKE_ARCHIVE="cmake-${CLANG_VERSION}.src.tar.xz"
 LIBUNWIND_ARCHIVE="libunwind-${CLANG_VERSION}.src.tar.xz"
 RUNTIMES_ARCHIVE="runtimes-${CLANG_VERSION}.src.tar.xz"
+THIRD_PARTY_ARCHIVE="third-party-${CLANG_VERSION}.src.tar.xz"
 CMAKE_ARCHIVE="cmake-${CMAKE_VERSION}.tar.gz"
 NASM_ARCHIVE="nasm-${NASM_VERSION}.tar.bz2"
 
@@ -96,6 +97,7 @@ LLVMCMAKE_BASE_URL="https://github.com/llvm/llvm-project/releases/download/llvmo
 LLD_BASE_URL="https://github.com/llvm/llvm-project/releases/download/llvmorg-${CLANG_VERSION}"
 LIBUNWIND_BASE_URL="https://github.com/llvm/llvm-project/releases/download/llvmorg-${CLANG_VERSION}"
 RUNTIMES_BASE_URL="https://github.com/llvm/llvm-project/releases/download/llvmorg-${CLANG_VERSION}"
+THIRD_PARTY_BASE_URL="https://github.com/llvm/llvm-project/releases/download/llvmorg-${CLANG_VERSION}"
 CMAKE_BASE_URL="https://cmake.org/files/v${CMAKE_VERSION%.*}"
 NASM_BASE_URL="https://www.nasm.us/pub/nasm/releasebuilds/${NASM_VERSION}"
 
@@ -104,7 +106,8 @@ ALL_ARCHIVES="$GMP_BASE_URL/$GMP_ARCHIVE $MPFR_BASE_URL/$MPFR_ARCHIVE $MPC_BASE_
 	$LLD_BASE_URL/$LLD_ARCHIVE $LLVM_BASE_URL/$LLVM_ARCHIVE $CLANG_BASE_URL/$CLANG_ARCHIVE \
 	$LLVMCMAKE_BASE_URL/$LLVMCMAKE_ARCHIVE $CRT_BASE_URL/$CRT_ARCHIVE $CTE_BASE_URL/$CTE_ARCHIVE \
 	$LIBUNWIND_BASE_URL/$LIBUNWIND_ARCHIVE $RUNTIMES_BASE_URL/$RUNTIMES_ARCHIVE \
-	$CMAKE_BASE_URL/$CMAKE_ARCHIVE $NASM_BASE_URL/$NASM_ARCHIVE $LIBSTDCXX_BASE_URL/$LIBSTDCXX_ARCHIVE"
+	$THIRD_PARTY_BASE_URL/$THIRD_PARTY_ARCHIVE $CMAKE_BASE_URL/$CMAKE_ARCHIVE \
+	$NASM_BASE_URL/$NASM_ARCHIVE $LIBSTDCXX_BASE_URL/$LIBSTDCXX_ARCHIVE"
 
 # GCC toolchain directories
 GMP_DIR="gmp-${GMP_VERSION}"
@@ -125,6 +128,7 @@ CTE_DIR="clang-tools-extra-${CLANG_VERSION}.src"
 LLVMCMAKE_DIR="cmake-${CLANG_VERSION}.src"
 LIBUNWIND_DIR="libunwind-${CLANG_VERSION}.src"
 RUNTIMES_DIR="runtimes-${CLANG_VERSION}.src"
+THIRD_PARTY_DIR="third-party-${CLANG_VERSION}.src"
 CMAKE_DIR="cmake-${CMAKE_VERSION}"
 NASM_DIR="nasm-${NASM_VERSION}"
 
@@ -953,6 +957,7 @@ build_LLVM() {
 	ln -nsf "$LLVMCMAKE_DIR" ../cmake
 	ln -nsf "$LIBUNWIND_DIR" ../libunwind
 	ln -nsf "$RUNTIMES_DIR" ../runtimes
+	ln -nsf "$THIRD_PARTY_DIR" ../third-party
 
 	$CMAKE -G "Unix Makefiles" \
 		-DCMAKE_INSTALL_PREFIX="$DESTDIR$TARGETDIR" \
@@ -1109,7 +1114,7 @@ case "$PACKAGE" in
 	CLANG|clang)
 		NAME="LLVM clang"
 		LLVM_VERSION=${CLANG_VERSION}
-		PACKAGES="CMAKE LLVM CLANG CRT CTE LLVMCMAKE LLD LIBUNWIND RUNTIMES"
+		PACKAGES="CMAKE LLVM CLANG CRT CTE LLVMCMAKE LLD LIBUNWIND RUNTIMES THIRD_PARTY"
 		CMAKE=${DESTDIR}${TARGETDIR}/bin/cmake
 		;;
 	IASL|iasl)
diff --git a/util/crossgcc/patches/clang-18.1.8.src_x86_baremetal.patch b/util/crossgcc/patches/clang-18.1.8.src_x86_baremetal.patch
deleted file mode 100644
index 61c608cbbe..0000000000
--- a/util/crossgcc/patches/clang-18.1.8.src_x86_baremetal.patch
+++ /dev/null
@@ -1,29 +0,0 @@
-diff --git a/lib/Driver/ToolChains/BareMetal.cpp b/lib/Driver/ToolChains/BareMetal.cpp
-index 852e0442..eb84a785 100644
---- a/lib/Driver/ToolChains/BareMetal.cpp
-+++ b/lib/Driver/ToolChains/BareMetal.cpp
-@@ -169,6 +169,12 @@ static bool isPPCBareMetal(const llvm::Triple &Triple) {
-          Triple.getEnvironment() == llvm::Triple::EABI;
- }
-
-+/// Is the triple x86_32 or x86_64 -*-none-elf?
-+static bool isX86BareMetal(const llvm::Triple &Triple) {
-+  return Triple.isX86() && Triple.getOS() == llvm::Triple::UnknownOS &&
-+    Triple.getEnvironmentName() == "elf";
-+}
-+
- static void findMultilibsFromYAML(const ToolChain &TC, const Driver &D,
-                                   StringRef MultilibPath, const ArgList &Args,
-                                   DetectedMultilibs &Result) {
-@@ -234,9 +240,10 @@ void BareMetal::findMultilibs(const Driver &D, const llvm::Triple &Triple,
-
- bool BareMetal::handlesTarget(const llvm::Triple &Triple) {
-   return isARMBareMetal(Triple) || isAArch64BareMetal(Triple) ||
--         isRISCVBareMetal(Triple) || isPPCBareMetal(Triple);
-+    isRISCVBareMetal(Triple) || isPPCBareMetal(Triple) || isX86BareMetal(Triple);
- }
-
-+
- Tool *BareMetal::buildLinker() const {
-   return new tools::baremetal::Linker(*this);
- }
diff --git a/util/crossgcc/patches/clang-21.1.8.src_x86_baremetal.patch b/util/crossgcc/patches/clang-21.1.8.src_x86_baremetal.patch
new file mode 100644
index 0000000000..809b290339
--- /dev/null
+++ b/util/crossgcc/patches/clang-21.1.8.src_x86_baremetal.patch
@@ -0,0 +1,25 @@
+diff -u a/lib/Driver/ToolChains/BareMetal.cpp b/lib/Driver/ToolChains/BareMetal.cpp
+--- a/lib/Driver/ToolChains/BareMetal.cpp
++++ b/lib/Driver/ToolChains/BareMetal.cpp
+@@ -51,6 +51,12 @@
+          Triple.getEnvironment() == llvm::Triple::EABI;
+ }
+ 
++/// Is the triple x86_32 or x86_64 -*-none-elf?
++static bool isX86BareMetal(const llvm::Triple &Triple) {
++  return Triple.isX86() && Triple.getOS() == llvm::Triple::UnknownOS &&
++    Triple.getEnvironmentName() == "elf";
++}
++
+ static bool findRISCVMultilibs(const Driver &D,
+                                const llvm::Triple &TargetTriple,
+                                const ArgList &Args, DetectedMultilibs &Result) {
+@@ -351,7 +357,7 @@
+ bool BareMetal::handlesTarget(const llvm::Triple &Triple) {
+   return arm::isARMEABIBareMetal(Triple) ||
+          aarch64::isAArch64BareMetal(Triple) || isRISCVBareMetal(Triple) ||
+-         isPPCBareMetal(Triple);
++         isPPCBareMetal(Triple) || isX86BareMetal(Triple);
+ }
+ 
+ Tool *BareMetal::buildLinker() const {
diff --git a/util/crossgcc/sum/clang-18.1.8.src.tar.xz.cksum b/util/crossgcc/sum/clang-18.1.8.src.tar.xz.cksum
deleted file mode 100644
index a517ab901a..0000000000
--- a/util/crossgcc/sum/clang-18.1.8.src.tar.xz.cksum
+++ /dev/null
@@ -1 +0,0 @@
-581e929ba0d9fafc555081ab18d8c3fdf4478ac2  tarballs/clang-18.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/clang-21.1.8.src.tar.xz.cksum b/util/crossgcc/sum/clang-21.1.8.src.tar.xz.cksum
new file mode 100644
index 0000000000..243e5e2616
--- /dev/null
+++ b/util/crossgcc/sum/clang-21.1.8.src.tar.xz.cksum
@@ -0,0 +1 @@
+052b4b826aba886d0a3fada696445d2fb1ffec88  tarballs/clang-21.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/clang-tools-extra-18.1.8.src.tar.xz.cksum b/util/crossgcc/sum/clang-tools-extra-18.1.8.src.tar.xz.cksum
deleted file mode 100644
index 6b9b67cb64..0000000000
--- a/util/crossgcc/sum/clang-tools-extra-18.1.8.src.tar.xz.cksum
+++ /dev/null
@@ -1 +0,0 @@
-32923b812700526b76451384e4662ca45360d564  tarballs/clang-tools-extra-18.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/clang-tools-extra-21.1.8.src.tar.xz.cksum b/util/crossgcc/sum/clang-tools-extra-21.1.8.src.tar.xz.cksum
new file mode 100644
index 0000000000..0e31f14c51
--- /dev/null
+++ b/util/crossgcc/sum/clang-tools-extra-21.1.8.src.tar.xz.cksum
@@ -0,0 +1 @@
+2429c7b1836e6db177e26cf4c85b5a817cda7c62  tarballs/clang-tools-extra-21.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/cmake-18.1.8.src.tar.xz.cksum b/util/crossgcc/sum/cmake-18.1.8.src.tar.xz.cksum
deleted file mode 100644
index d0e63313d9..0000000000
--- a/util/crossgcc/sum/cmake-18.1.8.src.tar.xz.cksum
+++ /dev/null
@@ -1 +0,0 @@
-1ea03e355b705b4cada3051bd7301a57daa19283  tarballs/cmake-18.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/cmake-21.1.8.src.tar.xz.cksum b/util/crossgcc/sum/cmake-21.1.8.src.tar.xz.cksum
new file mode 100644
index 0000000000..6317498355
--- /dev/null
+++ b/util/crossgcc/sum/cmake-21.1.8.src.tar.xz.cksum
@@ -0,0 +1 @@
+da308aa4c0e80835e123771ebe3e5fbfc5244a45  tarballs/cmake-21.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/compiler-rt-18.1.8.src.tar.xz.cksum b/util/crossgcc/sum/compiler-rt-18.1.8.src.tar.xz.cksum
deleted file mode 100644
index 711ef353c4..0000000000
--- a/util/crossgcc/sum/compiler-rt-18.1.8.src.tar.xz.cksum
+++ /dev/null
@@ -1 +0,0 @@
-6ecbfa5516b60adb4e4e60f991b0d8ddf5aab12a  tarballs/compiler-rt-18.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/compiler-rt-21.1.8.src.tar.xz.cksum b/util/crossgcc/sum/compiler-rt-21.1.8.src.tar.xz.cksum
new file mode 100644
index 0000000000..2362125c5a
--- /dev/null
+++ b/util/crossgcc/sum/compiler-rt-21.1.8.src.tar.xz.cksum
@@ -0,0 +1 @@
+141a3877eedd036349feaddc0d303abeeff96b6c  tarballs/compiler-rt-21.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/libunwind-18.1.8.src.tar.xz.cksum b/util/crossgcc/sum/libunwind-18.1.8.src.tar.xz.cksum
deleted file mode 100644
index d3819e303a..0000000000
--- a/util/crossgcc/sum/libunwind-18.1.8.src.tar.xz.cksum
+++ /dev/null
@@ -1 +0,0 @@
-5bee6cd2847f6d468861c78a21236e1c6fdc8374  tarballs/libunwind-18.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/libunwind-21.1.8.src.tar.xz.cksum b/util/crossgcc/sum/libunwind-21.1.8.src.tar.xz.cksum
new file mode 100644
index 0000000000..6b0516a6b2
--- /dev/null
+++ b/util/crossgcc/sum/libunwind-21.1.8.src.tar.xz.cksum
@@ -0,0 +1 @@
+c71485804e2a8e531469ee461fc312218686d641  tarballs/libunwind-21.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/lld-18.1.8.src.tar.xz.cksum b/util/crossgcc/sum/lld-18.1.8.src.tar.xz.cksum
deleted file mode 100644
index 490a83596e..0000000000
--- a/util/crossgcc/sum/lld-18.1.8.src.tar.xz.cksum
+++ /dev/null
@@ -1 +0,0 @@
-1cf1fa9848b05a07d3d52e69949d44003f2ab2af  tarballs/lld-18.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/lld-21.1.8.src.tar.xz.cksum b/util/crossgcc/sum/lld-21.1.8.src.tar.xz.cksum
new file mode 100644
index 0000000000..6e98bb89dc
--- /dev/null
+++ b/util/crossgcc/sum/lld-21.1.8.src.tar.xz.cksum
@@ -0,0 +1 @@
+c41039defb66d59d292567fe1d3e4d28fc2dec70  tarballs/lld-21.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/llvm-18.1.8.src.tar.xz.cksum b/util/crossgcc/sum/llvm-18.1.8.src.tar.xz.cksum
deleted file mode 100644
index 4845fb5b01..0000000000
--- a/util/crossgcc/sum/llvm-18.1.8.src.tar.xz.cksum
+++ /dev/null
@@ -1 +0,0 @@
-f9befa4cbef3f688ab48fca42449e13c5bcb872d  tarballs/llvm-18.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/llvm-21.1.8.src.tar.xz.cksum b/util/crossgcc/sum/llvm-21.1.8.src.tar.xz.cksum
new file mode 100644
index 0000000000..a4ca09f05e
--- /dev/null
+++ b/util/crossgcc/sum/llvm-21.1.8.src.tar.xz.cksum
@@ -0,0 +1 @@
+5aea9c8a3b1f1fa7ddebc2d2cc6742d4a1ee569e  tarballs/llvm-21.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/runtimes-18.1.8.src.tar.xz.cksum b/util/crossgcc/sum/runtimes-18.1.8.src.tar.xz.cksum
deleted file mode 100644
index fbee9941d1..0000000000
--- a/util/crossgcc/sum/runtimes-18.1.8.src.tar.xz.cksum
+++ /dev/null
@@ -1 +0,0 @@
-4a5ea2f22b2d81467e739f4b070cf7ff52785856  tarballs/runtimes-18.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/runtimes-21.1.8.src.tar.xz.cksum b/util/crossgcc/sum/runtimes-21.1.8.src.tar.xz.cksum
new file mode 100644
index 0000000000..0022a20757
--- /dev/null
+++ b/util/crossgcc/sum/runtimes-21.1.8.src.tar.xz.cksum
@@ -0,0 +1 @@
+2edc085c606ef464cde44b5cbfb5727c59ae2fd3  tarballs/runtimes-21.1.8.src.tar.xz
diff --git a/util/crossgcc/sum/third-party-21.1.8.src.tar.xz.cksum b/util/crossgcc/sum/third-party-21.1.8.src.tar.xz.cksum
new file mode 100644
index 0000000000..654980e1a1
--- /dev/null
+++ b/util/crossgcc/sum/third-party-21.1.8.src.tar.xz.cksum
@@ -0,0 +1 @@
+a1a50bb1f6a02aa82ef6de5942b164061f9acbc4  tarballs/third-party-21.1.8.src.tar.xz